A critical concept in physics and engineering is Superposition: the net (total) effect on a system is the sum of all component effects.

The "ideal" system is still there in any real physical system. It is not invalid in the slightest. The idealization is simply being modified by an infinite number of other smaller forces and interactions (friction, air resistance, earth rotation, etc) that cannot be easily quantified at your level. Once you learn the idealization, you can use superposition to add more components later on.